Live chats on Niconico flow across the screen which mean viewers won't have to move their eyes away from the video.
One extension best for this function that I have found is called Youtube Live Chat Flow. The chat appears beautifully on the screen with colors that help to distinguish guest, member, moderator, owner and us.
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This extension is very recommended also because the chat flows very smoothly
without jittery. Text is also customizable to our preference such as size,
appear duration, outline thickness, etc.
Go to link below to download and install the extension and to read more on the
extension.
Read also : Watch Multiple Youtube Videos at Once
Reference: Reddit